There are many sorceries in Dark Souls. You need to obtain all of them for this achievement. Most of them are purchased from various merchants around Lordran. Below is a list of all the merchants in the game and how to find them or get them to sell the sorceries. The merchants that sell them (and their location/storyline) are below.

Big Hat Logan
Griggs of Vinheim
Dusk of Oolacile

Merchant Sold Spells

Aural Decoy - Sold by Griggs of Vinheim.
Fall Control - Sold by Griggs of Vinheim.
Great Heavy Soul Arrow - Sold by Griggs of Vinheim/Big Hat Logan.
Great Soul Arrow - Sold by Griggs of Vinheim/Big Hat Logan.
Heavy Soul Arrow - Sold by Griggs of Vinheim/Big Hat Logan/Rickhert of Vinheim.
Homing Soulmass- Sold by Griggs of Vinheim (only after Logan leaves)
Magic Shield - Sold by Griggs of Vinheim/Big Hat Logan.
Magic Weapon - Sold by Griggs of Vinheim/Big Hat Logan.
Soul Spear - Sold by Griggs of Vinheim.
Soul Arrow - Sold by Griggs of Vinheim/Big Hat Logan/Rickhert of Vinheim.
Hidden Body - Sold by Dusk of Oolacile.
Cast Light - Sold by Dusk of Oolacile.
Repair - Sold by Dusk of Oolacile.
Chameleon - Sold by Dusk of Oolacile.
Hidden Weapon - Sold by Dusk of Oolacile.
Crystal Magic Weapon - Sold by Big Hat Logan, but only after he's moved to Duke's Archives. See herefor how to make him go there.
Crystal Soul Spear - Sold by Big Hat Logan, but only after he's moved to Duke's Archives. See here for how to make him go there.
Homing Crystal Soulmass - Sold by Big Hat Logan, but only after he's moved to Duke's Archives. Seehere for how to make him go there.
Resist Curse - Sold by Ingward (the guy in the Crimson armor set in New Londo Ruins. He is on top of the church and will give you the Key to the Seal while you are there).
Enemy dropped/looted spells

Great Magic Weapon - Found on a corpse on the chandelier in the room full of Painting Guardians in Anor Londo. You must break the chain while you are walking on the beams overhead for it to come down.
Hush - Dropped by Griggs of Vinheim (after you purchase everything from him, he will go here. Kill him and he'll drop it.) OR it can be found on a corpse along with the Black Sorcerer Set and the Slumbering Dragoncrest Ring. When you get to the room with the stone launching mechanism, launch it in another direction and go down the way you came. Then halfway down, drop onto the pillar and pick it up off the corpse.
Remedy - Found in a chest in Blighttown near the elevator. The quickest way to get there is the shortcut from the Valley of Drakes. Descend several ladders and watch out for a path on a root with some woods. Follow that root to the other side, past the cragspider, and directly next to a corpse will be the treasure chest with this spell.
Strong Magic Shield - Treasure from a chest in the Duke's Archives. Located at the top floor, at the far end of the walkway near the Channeler (requiring the rotating stairs to get to).
White Dragon Breath - Dropped by Big Hat Logan AT THE END OF HIS STORYLINE. See HERE for how to do this.